package demo1;

public class MyLinkedList {
    public static class ListNode {
        public int val;
        public ListNode prev;
        public ListNode next;

        public ListNode(int val) {
            this.val = val;
        }
    }
    public ListNode head;
    public ListNode last;
    //合并两个有序的
    public ListNode mergeTwoLists(ListNode list1, ListNode list2) {

    }
    //头插法
    public void addFirst(int data){
        ListNode node = new ListNode(data);
        if(head == null){
            head = node;
            last = node;
        }else {
            node.next = head;
            head.prev = node;
            head = node;
        }
    }
    //尾插法
    public void addLast(int data){
        ListNode node = new ListNode(data);
        if(head == null){
            head = node;
            last = node;
        }else {
            last.next = node;
            node.prev = last;
            last = node;
        }
    }
    //任意位置插入,第一个数据节点为0号下标
    public void addIndex(int index,int data){
        int ret = size();
        if(index < 0 || index > ret){
            return;
        }
        if(index == 0){
            addFirst(data);
            return;
        }
        ListNode cur = head;
        for(int i = 0; i < index; i++){
            cur = cur.next;
        }
        ListNode node = new ListNode(data);
        node.next = cur;
        node.prev = cur.prev;
        cur.prev.next = node;
        cur.prev = node;
    }
    //查找是否包含关键字key是否在单链表当中
    public boolean contains(int key){
       ListNode cur = head;
       while(cur != null){
           if(cur.val == key){
               return true;
           }
           cur = cur.next;
        }
       return false;
    }
    //删除第一次出现关键字为key的节点
    public void remove(int key){
      ListNode cur = head;
      while(cur != null){
          if(cur.val == key){
              if(cur == head){
                  head = head.next;
                  if(head.next == null){
                      last = null;
                  }else {
                      head.prev = null;
                  }
                  return;
              }else if(cur.next == null){
                  last = last.prev;
                  cur.prev.next = null;
                  return;
              }else {
                  cur.prev.next = cur.next;
                  cur.next.prev = cur.prev;
              }
          }
          cur = cur.next;
      }
    }
    //删除所有值为key的节点
    public void removeAllKey(int key){
        ListNode cur = head;
        while(cur != null){
            if(cur.val == key){
                if(cur == head){
                    head = head.next;
                    if(head.next == null){
                        last = null;
                    }else {
                        head.prev = null;
                    }
                }else if(cur.next == null){
                    last = last.prev;
                    cur.prev.next = null;
                }else {
                    cur.prev.next = cur.next;
                    cur.next.prev = cur.prev;
                }
            }
            cur = cur.next;
        }
    }
    //得到单链表的长度
    public int size(){
        int count = 0;
        ListNode cur = head;
        while(head != null){
            head = head.next;
            count++;
        }
        return count;
    }
    public void display(){
       ListNode cur = head;
       while(cur != null){
           System.out.print(head.val + " ");
           cur = cur.next;
       }
        System.out.println();
    }

    public void clear(){
     while(head != null){
         ListNode curN = head.next;
         head.prev = null;
         head.next = null;
         head = curN;
     }
     head = null;
     last = null;
    }

}
